From - Thu Jan 29 14:54:42 1998 From: amlaukka@cc.helsinki.fi (Aki M Laukkanen) Newsgroups: comp.sys.amiga.programmer,de.comp.sys.amiga.misc Subject: Re: DOOMPORTERS: 040/060 wall slow Date: 23 Jan 1998 21:20:50 GMT Organization: University of Helsinki Lines: 27 Message-ID: References: <6ab2iv$61$1@Nordschleife.modem.informatik.tu-muenchen.de> NNTP-Posting-Host: vesuri.helsinki.fi X-Newsreader: slrn (0.9.3.2 UNIX) Path: noticias.ulpgc.es!news.rediris.es!news.belnet.be!jussieu.fr!newsfeed.eerie.fr!news.maxwell.syr.edu!news.idt.net!fci-se!fci!newsfeed.sunet.se!news99.sunet.se!news01.sunet.se!193.166.5.150.MISMATCH!news.funet.fi!news.helsinki.fi!amlaukka Xref: noticias.ulpgc.es comp.sys.amiga.programmer:76134 de.comp.sys.amiga.misc:10194 In article <6ab2iv$61$1@Nordschleife.modem.informatik.tu-muenchen.de>, fischerj@informatik.tu-muenchen.de wrote: >and see the enormous difference between drawing walls on a 320 sized >screen and a 319 sized screen on 040 or 060. [the rest clipped] Yes, this is due to the characteristics and size of the datacache and the behaviour of the copyback cache operation. Writing vertically is generally a very bad thing(tm) with write-allocating copyback caches. If Doom in mind the width and how high is the wall are keyfactors. The four-way set-associative nature of the caches mandates the "optimal" width which shouldn't be a multiple of 16. One particularly bad case is a width of 256. I think there are couple of examples about this in some demos with say "voxel landscape" or "doom" effects. Considering ADoom there's the -mmu option which changes the cachemodel for the chunky buffer as write through so no cache lines are allocated at writes. The effect of this is about 10 percent speedup on M68060 and a little less on M68040. This can be explained by M68060 having the four entry store buffer where the writes can be buffered until bus is free. Currently also to minimize the counter effect of not having copyback the floor and ceiling is drawn with long word writes to long word aligned addresses. I plan to improve the "trick" so that floor and ceiling can be drawn with copyback on but sprites and walls aren't. -- D.